Drum grinding mill with discharge openings in the liner



Dec. 14, 1948. D. w. GATES DRUM GRINDING MILL WITH DISCHARGE OPENINGS IN THE LINER 4 Sheets-Sheet 1 Filed March 17, 1945 D WEARING GATES 3nnentor Gttomeg Dec. 14, 1948. D, w, GATES 2,456,266

DRUM GRINDING MILL WITH DISCHARGE OPENINGS IN THE LINER Filed March 1'7, 1945 4 Sheets-Sheet 2 k l I /5 50 Q 39 lo Lu 1/ f D. WEARING GATES ZSnventor Gttornegs Dec. 14, 1948. D. w. GATES DRUM GRINDING MILL WITH DISCHARGE OPENINGS IN THE LINER 4 Sheets-Sheet 3 Filed March 17, 1945 D.WE ARING GAT Eg (Ittorncxi:

D. W. GATES DRUM GRINDING MILL WITH DISCHARGE Dec. 14, 1948.

OPENINGS IN THE LINER 4 Sheets-Sheet 4 Filed March 17, 1945 hwy 4 4..

of WEARING GATES Jnventor flue/c Qttornegs Fatented Dec. 14, 1948 2,456,266 DRUM GRINDING MILL wrrnmscnAncE OPENINGS IN THE LINER D. Wearing Gates, Seattle, Wash., 'assignor to- G. B. & S. Mill, Ina, Yakima, Wash.

Application March 17, 1945, Serial No. 583,183

Claims.

This invention relates to a drum grinding mill with discharge openings in the liner and, more particularly, to a comminution method by which ore is crushed and ground upon itself within a revolving cylinder in closed circuit for particle sizing and a mechanism operable to practice said method.

In the field of mineral recovery there are many types of mechanisms employed to reduce mine run ore to a particle size suitable for later concentration methods commonly practiced. The principal purpose of these mechanisms is to produce fine sized particles of fairly uniform size to either liberate the mineral content from the waste rock with which it is associated, or to size it for flotation requirements, or to meet commercial product requirements, particularly in the.

field of non-metallic ores. In the past it has been customary to reduce ores from fairly large sized chunks to fine particles in two or more stages in which first the large chunks are reduced in primary crushing mills and then fed to secondary grinding mills. This has resulted in duplication of machinery, excessive power costs, slow operation, and other disadvantageous factors well known in the field. Sliming, or the formation of colloids, often occurs and produces material practically impossible to process for the recovering of the mineral content trapped therein, and is a total waste of both energy and ore values. The previous crushing mechanisms have usually employed grinding media in the form of hammers, balls, tubes or rods, in each of which type mills a foreign body is used to pound and grind the feed material. It is commonly recognized that large quantities of these foreign bodies, iron particles ordinarily, slough oil in the crushing and grinding operation and contaminate the discharged tailings. In addition, it must be seen that unnecessary energy is used in activating these foreign crushing media in order that suitable impacts or blows may beobtained to effect ore fracturing. Another difliculty arises in the art from the prior practice of crushing by a moving object being brought into impacting contact with a relatively immovable liner surface which results in the hammeringof rock particles into the mineral portion to the end that much mineral is discarded as waste product rather than be recovered with the values. Also there has been diiiiculty in the past in effecting peripheral discharge of the ground product in a continuous manner since the outlets have been subject of clogging and jamming to the end that the mills soon become inoperative until they are stopped and cleaned. These and other disadvantages have impeded the eflicient operation of ore processing plants for years andhave required that an operator invest needless sums of money in order to gain only a fair result.

Having in mind the defects of the prior art,

operable screening mechanism for regulating the size of the discharging material and so adapted as to return over-size particles for further crushing, all without impairing the function of grinding.

Still another object of my invention is to produce a grinding mill in which a minimum of overgrinding occurs and the formation of slimes or colloids is largely precluded.

One other object of the invention resides in the production of a grinding mill in which rupture of the feed material due to impact and abrasion produces a discharge of particles having surfaces formed of the lines naturally demarking ore and rock in the case of mineral bearing ores, which material is highly suited to treatment by flotation.

Other and further objects of the invention reside in the provision in a grindingmill of means whereby multiple blows from substantially opposite directions act upon the rock as it is crushed and ground; control of the mesh-size of the discharged product may be had at all times; and a continuous discharge through sizing openings will be maintained without clogging or stoppage.

The foregoing objects and others ancillary thereto I prefer to accomplish as follows:

According to a preferred embodiment of my invention, I mount a hollow cylinder for revolution about a horizontal axis provided by'suitable trunnion members journalled upon adjacent supports. Power is applied to one of the trunnions and the other is hollow for the continuous introduction of feed material. Around the inner periphery of the cylindrical shell, I loosely mount metallic liners, each having at least one lifting shelf. Between the liners and the inner surface of the shell is placed flexible material, such as a rubber sheet, or the like, which serves as a cushion between the liner and the shell. It is important that the liner be sectional and that the sections be spaced apart to provide exit slots for the material as it is crushed. By controlling the size of the spaces between the liner sections, a desired discharge size of the particles can be obtained. The cushion between the liners and the shell, and the shell itself, are ported adjacent the spaces Just described to permit the outward discharge tions of the material and cause it to be thrown to cascade onto the following material and the liners and, by impact, to crush the same. Simultaneously, an abrasion is taking place in the depths of the material in the cylinder to reduce the sizes of the particles by attrition. Means is provided for conveying feed material-to the mill and for receiving and removing the discharged crushed and ground material. Since it is ordinary practice to wet grind in this mill, water conduit means is provided for the delivery of that fluid to within the cylinder.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be'understood from the following description of a specific embodiment when read in connection with the accompanying drawings, in which:

Fig. 1 is a view in elevation of my grinding mill;

side of the supporting leg ll. Power is applied to shaft 24 through the instrumentality of gear 28, pinion 21, and motor 23, which constitute a power-reduction mechanism whereby the mill may be rotated at a relatively low speed. I have found it most practical to operate my mill at approximately 22 R. P. M.

Secured between the walls I! and i3 is the annulus or shell ring 30, having outstanding edge flanges 3|, by which the annulus may be welded or bolted to the peripheral edges of walls I! or i3. At spaced points around its circumference, the ring 33 is ported at 33, these ports constituting slots extending substantially the entire width of the ring face, parallel to its axis. On either side gt openings 33 are provided paired openings Arcuate liner segments 38, 31, 38, and 39 are loosely mounted within the cylindrical drum, described, by means of spaced-apart ears 40 and 4i which are inserted through the openings 34 and and are there retained by means of a taper or key pin 42, that passes through the cars or 4!, as the case may be, and is secured by cotter pin 43.

I have described that ears 40 and 4| pass through the openings 34 and 35 respectively and it must be borne in mind that the flt between the ears and the openings through which they pass is a loose one, in other words, is such a loose fit that the ears may move within the openings and consequently, the liners will be to a degree loosely mounted within the annulus 30. Between the segments on their outer faces and the inner face of the annulus 30 I place flexible sheet material 44, such as rubber to provide a cushion between the individual liners and the adjacent wall of the drum to insure tension upon the liners and to dampen relative movement between the Fig. 2 is a cross-sectional view through the mill;

Fig. 3' is an enlarged sectional view of a pcripheral portion of the mill detailing the arrangement of parts;

Fig. 4 is a cross-sectional view taken on the plane of lines 4-4 of Fig. 3;

Fig. 5 is a detail sectional view of a portion of the peripheral screen showing the manner of clamping the same to the grinding cylinder; and

Fig. 6 is a vertical sectional view taken through the mill on lines 3-8 of Fig. 2.

Referring to the drawings, it will be seen that the grinding mill is formed as a cylinder mounted to rotate upon supports l0 and Ii about a horizontal axis and comprises the front wall i2, and the parallel spaced-apart rear wall l3 that are trunnioned on the supports. Upon the front wall is thehollow trunnion 14 attached by means of flanges l5 wlthbolts l3 cooperating with the annular wall II. The trunnion l4 constitutes both a support for the mill and also provides a hollow passage to permit the axial feeding material to the mill. Trunnion I4 is cradled in a plurality of rollers 20 upon which the bearing surface 2! of the trunnion rests. Rollers 20 are mounted in casing 22 that is secured to the topside of support It.

On the opposite side of the mill, the annular wall I3 is attached to the flange 23 which is secured to trunnion shaft 24, Journalled for rotation in bearing 25 which is mounted on the topliners and the supporting drum.

As can best be seen in Fig. 3 a space 46 is left between the ends of the liner segments, in this example 36 and 33, and it is through this space that finely ground material passes outwardly from the grinding zone within the drum to a straining zone peripherally therearound. To

vary the size of the spacing removable shims 41, held in place by bolts 48, may be attached to one or the other end of a liner segment in the manner disclosed in Fig. 3.

, Eachof the segments 38, 31, 38 and 39 is shown as having a lifting shelf 50 which extends substantially axisward of the drum and serves both to lift material within the drum and to act as an anvil under the material as it is crushed. The lip or inner edge of the shelf 50 is provided with a removable wear resisting edge portion 5| secured by the flange 52 and bolt 53 to the trailinside of the ledge to permit ready replacement oi the lip as it may wear during use of the mill.

It should be seen that the opening 46 is substantially aligned with the opening 33 and also that the rubber cushion 44 is ported at 54 so that material passing outwardly through the opening 46 can escape through the opening 33 to exterior of the drum.

As can best be seen in Fig. 4 the inner surfaces of the various liners 36, 31, 33 and 39, are concave longitudinally of the axis of the drum so that the intermediate low point 49' can serve during rotation of the drum to urge material within the drum to a, substantially central position thereof and away from the interior sidewalls of the drum. This latter arrangement eliminates wear on the inner side walls.

The outer edges of the'walls l2 and I3 circumierentially outward from the location of the annulus 30, are offset or flanged at 60,- to provide mounting means for screen 62 which peripherally encloses an annular shaped area surrounding the.

outside oi shell 30. Material passing outwardly between the ends of the liners and through the slot 33 of the shell is deposited upon the screen 62 and as the latter revolves in its circular path this materiel tumbles and falls on the screen, and, thereby, the particles smaller than the screen pass outwardly of the drum. The oversize particles within the screening zone or onv the inner surface of the screen eventually travel to a deflector blade 64 which is placed between annulus 30 and screen 62 and between the oflset peripherel walls I2 and I3 to dam up the flow of the oversize material and to direct it to move into v the return feed passage 65 whereby it is conducted to the return inlet 66 for regrinding within the mill. One or more such return passages may be used as required.

The mill is entirely enclosed by an apron in the rubber mounting and the energy therein stored is subsequently given of! when the force producing the compression is expended, and .ja secondar crushing blow axisward occurs. It has been found that it such were not the case relatively little crushing occurred. It is important located in advance of a lifting ledge 50' as it revolves. The lifting ledges thus serve two functions, one of=forming the pockets, and the other having edge flanges II to prevent the escape of the fines passing through screen 62 and also to prevent undue splashing of the water that may be used during the grinding operation. At its lower portion the apron I0 is connected with a hopper l2 and the fine material falls down in the hopper to the elevator tube 74 up which it is moved by the conveyor bucket I6 on the 'endless bent 'I'I for disposal as may be desired. In Fig. 1

the upper portion of apron 10 is broken away for convenience of illustration.

The feed material may be introduced through the hollow trunnion I4 with retprn feed through the instrumentality of the feed hopper 18 shown in Figs. 1 and 2. Water may be introduced to the interior of the mill through the conduit 80.

In this mill a hydro-sizing effect is obtained for the purposes of classification of the finished product. The amount of water caused to pass through the mill efiects a direct control upon the mesh size of particles being produced by crushing and attrition. In practice, where it is desired to produce an excess of fines, lesser amounts of water are employed as compared with those circumstances where greater quantities of oversized particles are desired. In the latter instance more water is used and less fines result due, it is believed, to the flushing effect of the passage of the water through the mill. It will be understood that this description applies to any given screen having predetermined openings therein. Naturally, this effect may be varied by employing coarser or finer screen with respect to which inlet water control may also be exercised.

It has been found that the play or movement of the liner segments obtained by reason of the resilient mounting means and by reason of the fact that the segments are out of contact with each other, insures the continuous discharge of the ground material through the slots between the liner segments. Flexibility in the slots is an important object of the invention and serves to cause the outward passage through theslots offlne materials which might otherwise clog and jam the slot openings and restrict discharge of the various particles.

, An additional function in the operation of this mill is ascribed to the rebound eflect obtained by the resilient mounting of the liner segments. As the rock being crushed descends upon and strikes the liner segments a compression occurs of lifting rock to a point where it is dumped to impact upon another such pocket in sequence therebehind. Because of the flexible box mountings between the liner segments and the cylinder, and through vibration of the mechanism, agitation of the rock is obtained in each of the pockets, which produces the settling of fine particles to the bottom of the pocket. The bottom of each pocket has a sizing opening discharging outward from.

the cylinder and the'walls of each suchopening 46 are relatively movable during operation of the mill and can function to knead the fines settling to they bottom of the pocket from inside the grinding cylinder to outside of it. This kneading action greatly enhances the discharge of the fines in the pocket without undue abrasion or other unnecessary reduction in the size of the particles. At the same time, the kneading action prevents the piling up or jamming of particles in the opening, as would be the case were not the walls of the opening relatively movable. To the described kneading action may also be accredited an unusually high capacity in a mill'of this type, with a given power input, as well as a proper handling of the rock as it is ground.

While I have shown and described particular embodiments of my invention, it will occur to those skilled in the art that various changes and modifications may be made without department from the invention, and I, therefore, aim in the appendedjclaims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

Having thus described my invention, I claim:

1. A grinding mill, comprising: a drum mounted to rotate about its horizontal axis, the drum consisting of a shell ring and spaced wearresisting liner segments, the spaces between said segments serving as outlet openings for comminuted material, mountings for said segments, said mountings having loose engagement with the shell ring whereby on rotation of the drum a limited movement is imparted to said segments thereby preventing clogging of the material therebetween, and a resilient mounting between each segment and the shell ring to effect a rebound of particles striking the liner.

2. A grinding mill, comprising: a drum mounted to rotate about its horizontal axis, the drum consisting of a shell ring and spaced wear-resisting liner segments, the spaces between said segments serving as outlet openings for comminuted material, mountings for said segments, said mountings having loose engagement with the shell ring whereby on rotation of the drum a limited movement is imparted to said segments thereby preaeaaaoa venting clogging oi the material therebetween, and a resilient filler pad between each segment and the shell ring to efleot a rebound 01' particles striking the liner.

3. A grinding mill, comprising: a drum mounted to rotate about its horizontal axis, the

drum consisting of a shell ring and spaced wearresisting liner segments, the spaces between said segments serving as outlet openings for comminuted material, mountings for said segments, said mountings having loose engagement with the shell ring whereby on rotation of the drum a limited movement is imparted to said segments thereby preventing clogging of the material therebetween, and a rubber mounting between each segment and the shell ring to effect a rebound of particles striking the liner.

4. A grinding mill, comprising: a drum mounted to rotate about its horizontal axis, the drum consisting 01 a shell ring and spaced wearresisting liner segments, the spaces between said segments serving as outlet openings ior comminuted material, mountings for said segments, said mountings having loose engagement with the shell ring whereby on rotation of the drum a limited movement is imparted to said segments thereby preventing clogging of the material therebetween, a resilient mounting between each segment and the shell ring to effect a rebound of particles striking the liner, and a lifting shelf within said ground and to drop the same.

Number Name Date 39,899 Dickey Sept. 16, 1863 143,745 Bradford Oct. 21, 1873 681,983 Schoellhorn et al. Sept. 3, 1901 1,343,292 Turner June 15, 1920 1,441,584 Isbell Jan. 9, 1923 1,538,620 Cancla May 19, 1925 FOREIGN PATENTS 30 Number Country Date 331 Great Britain Oct. 18, 1906 5. A grinding mill, comprising: a drum mounted to otate about its horizontal axis, the drum oonsisnng of a, shell ring and spaced wearreslsting liner segments, the spaces between said segments serving as outlet openings for commi-' nuted material, mounting ears on each of said segments, said mounting ears being in loose engagement with the shell ring whereby on rotation of the drum a limited movement is imparted to said segments thereby preventing clogging of the material therebetween, and a resilient mounting between the segments and the shell ring to eflect a rebound of particles striking the liner.

D. WEARING GATES.

REFERENCES CITED The iollowing-reterences are of record in the file of this patent:

UNITED STATES PATENTS 

